Welding control system



March 1941- e. HAGEDORN ETAL 4 1 7 WELDING CONTROL SYSTEM Filed. June 14, 1939 Patented Mar. 4, 1941 v UNITED STATES PATENT OFFICE WELDING CONTROL SYSTEM I Gerhard Hagcdorn, Berlin-Lichterfeide, Erwin Luxer, Berlin-Sudende, and Ernst-Gunther Wahl, Berlin-Steglitz, Germany, assignors to Vertriebsgesellschaft des Leipziger Leichtmetallwerk m. b. H., Berlin-Lankwitz, Germany Application June 14, 1939, Serial No. 279,218

In Germany June 18, 1938 a 1 Claim.

mechanical switches are arranged in the grid-.

small switching power of these circuits, there is not produced any substantial electric arcing or burning, so that even energy impulses of very short duration can be accurately determined. In this way the speed of the variation of the generator field becomes of increased importance, more particularly in the case of light metal spot and seam welding, since it is the speed which sets a limit to the shortening of the duration of the energy in the case of full generator power.

In carrying out the invention use is preferably made of a source of continuous current voltage for the excitation of the medium or high frequency generator and of a gas or vapour discharge tube for the time switch. It is an advantage to use for the switching on or of! of the continuous current circuit of the excitation of the medium or high frequency current generator one or more grid-controlled gas or vapour discharge tubes, in which one or more auxiliary electric arcs fed by continuous current are produced and main-.

tained. The switching on of the continuous current circuit is effected by applying a positive voltage to the grid, and a switching off thereof is effected by first applying a negative voltage to the grid and thereupon either reversing the polarity of the anode voltage or reducing it for a short period of time, by connecting in parallel with the main discharge charged or non-charged condensers.

In the arrangement according to the present invention, only a small fraction 01' this power has to be switched on and off. More particularly the switching tube is very small, so that the welding apparatus can easily be transported. Moreover, by the means described, medium and high frequency currents can be indirectly switched on and d, which can be carried out with the known welding timing arrangements, only up to a few hundred cycles per second. The use of higher ire quency means that a smaller and lighter welding transformer can be employed, which can in many cases then be brought nearer to the welding point, whereby a further economy in power is effected. The simplicity of this new arrangement will be apparent from the diagram of connections.

Referring to the accompanying drawing, the invention is illustrated by way of example in connection with a diagram of connections of an electrical welding installation comprising a medium or high frequency welding generator excited from a source of continuous current through a switching tube.

The drawing shows a medium or high frequency impulse generator used in a resistance welding installation, in which the magnetic circuits are constituted throughout by laminated iron, and in which the excitation current is derived from a source of continuous current voltage. The welding generator I is driven by a motor 2 and is mechanically coupled with the excitation machine 3. The two electrodes 6 and 1 rest on the metal sheets 4 and 5 to be welded together, and the electrodes are connected to the secondary winding 8 of the welding tranformer 9. The primary winding l0 carrying the higher voltage is connected to the armature winding ll 01' the welding generator. The excitation winding H of the welding generator is connected to the armature of the continuous current excitation machine 3 through the cathode l3, anode ll of the switching tube I5 and a regulating resistance 1 6. The source of continuous current voltage I! supplies the current for the auxiliary arc of the tube l5 through the regulating resistance I8 and the auxiliary anode IS. The other terminal of the battery I! is connected to the cathode l3 of the switching tube. For the starting of the auxiliary electric are use is, for instance, made of a starting pin 20, which is connected to the positive terminal of the source of current i! through the switch 2| and the regulating resistance 22. During the intervals of rest of the excitation current the two controlling grids 23 and 2d are biased, through the two grid resistances 25 and 26, and the two resistances 2'! and 28 connected to the source of grid voltage "Z9, to a stopping potential which is negative with respect to the cathode. The positive terminal of the source of voltage 23 is connected to the cathode it of the switching tube. i/Then the excitation current of the welding generator has to be switched on, switch is operated, whereby a circuit including the positive terminal oi the source of grid voltage ti, switch 3d, capacity 32, resistance ill, and the negative terminal of the source of grid voltage ii is closed. At the first-moment the voltage on the condenser 32 is substantially zero and the grid 23 receives a positive voltage impulse and starts the main discharge in the tube i5 ionised by the auxiliary electric arc. As soon as the charging of the condenser 32 is teririindtei, the again biased to its orig" In order to interrupt ,j therewith the cxcitution generator, a switch 33 i circuit including the {it source oi grid vi'iltiig iii reisistance 28, end the 11 source of grid "volts {e M 1n the case iltiiii'fl'ibm moved, so that now also the since, at this nioinerit it has Wi "i. respect to t, it: cathode l3 9. potential which is higher than that of the anode H by the voltage drop on the reg1iiating resistance i8. At the same time the discharge current of the extinguishing capacity 35 is superposed on the two anode currents in the direction of the positive condenser plates, anode 35, cathode l3, anode H, and negative condenser plates, in this way effecting the extinguishing oi the are between the anode I4 and cathode H3. The negative voltage on the grid 23 prevents the restarting of this path. The resistance 31 is so large that the discharge of the current flowing through it is extinguished at the anode 35 by the grid 24, which has again become the negative during the charging of the capacity 34, whereby id winding, o. discharge tithe he cathode and en cnode cornice-ted in said circuit eem if?! my oi the Welding grit cted i'ii'oin the erogzitziitiiimi o 1' so "iillE'E-i .urrent end it circuit i1 'i'ilivli for controlling the excitation oi said generator, ii grid biasing circuit for said tube including con denser and a, switch, a second anode Within said tube, ii. resistor connected to the second anode and said circuit, a condenser bridging said anodes, a second grid biasing circuit associated with the second anode, a condenser in said second grid circuit, and a second switch in the second grid circuit operated by said first switch.

GERHARD HAGEDORN. ERWIN LUXER. ERNST-GUNTKER wAnn 

